I read that there is a small probability that some of the insect eggs that remain on the grain from the field are not completely neutralized in processing. Would this be of practical concerns regarding oats, barley, and beans in America?

Grains and beans processed in the United States and most other countries are centrifuged to remove bugs, bug-eggs, and other debris before the food is sold in stores. The process known colloquially as"Entoleting", because the Entoleter Company is the leading supplier of the equipment used for this purpose is so effective that as long as grains are stored in cool and dry conditions they will remain bug-free for many months. For this reason, there is no need to check grains or beans for insect infestation in the United States. If you are using grains in another country or if you have reason to believe the grains may not have been stored properly, then you might want to contact a local Rabbi to determine if/how to check them for infestation.